1. Field of the Invention
The present invention relates to a video receiving apparatus and a video receiving method, which are suitable for being applied to a digital video/audio I/O interface standard referred to as the HDMI (High-Definition Multimedia Interface) standard.
2. Description of the Related Art
Lately, the HDMI standard has been developed as an interface standard to transmit uncompressed digital video data and the like between a plurality of video apparatuses. According to the HDMI standard, video data is transmitted as individual primary color data respectively transmitted based on a pixel. In the HDMI standard, audio data is also transmitted using a transmission line for video data in a blanking period of the video data. Red, green and blue (R-data, G-data, and B-data) of additive primary color data on three channels are transmitted. Alternatively, luminance and color-difference signals such as Y, Cb and Cr may be transmitted.
Data of respective colors basically includes eight bits in one pixel. Synchronization signals such as a horizontal synchronization signal and a vertical synchronization signal are also transmitted at a timing that each synchronization signal is arranged. A transmission line for pixel clock of video data and a transmission line for control data are also provided.
As described above, according to the HDMI standard, pixel-based video data is transmitted for each color, in which the number of pixels in one frame and a frame frequency are not limited to specific types. Therefore, a frame frequency of input video data or the like may need to be detected in a receiving apparatus that receives video data output from a video transmission apparatus through an HDMI standard cable and that performs reception processing in sync with the detected frame frequency and the like.
FIG. 1 is a schematic diagram showing a processing example of determining the type of input video data in an apparatus to receive the video data using a standard of related art. A signal received at a terminal (hereinafter, the terminal is referred to as an HDMI terminal in this specification) 1, to which a cable of the HDMI standard is connected, is supplied to an HDMI information acquisition unit 2 where the signal multiplexed on each line is separated, and the separated signal is supplied to a signal detection unit 3. Also, clock signal and synchronization signal components in the received signal obtained at the HDMI terminal 1 are supplied to a synchronization frequency analysis unit 4 so that the synchronization frequency is analyzed through processing of counting the clock signal and the like. Information on the analyzed synchronization frequency is supplied to the signal detection unit 3, in which the information is used for determining a type of the video signal.
FIG. 2 is a flow chart indicating an example of signal detection processing of related art which is performed at the signal detection unit 3 and peripheral circuits of the signal detection unit 3 with the configuration shown in FIG. 1. First, upon a signal input into the HDMI terminal 1, it is determined whether the input signal is in such a state that frequency information thereof can be received stably (step S1). When it is determined that a signal is in a stable state, the signal type is determined from the information included in the received signal (step S2). Subsequently, a supplied clock signal is analyzed at the synchronization frequency analysis unit 4 in order to determine whether the frequency is within a preset acquisition range (step S3). In the case of detecting the frequency out of the acquisition range, it is determined that there is no signal input or the signal is out of the range, and video data is not output from the signal detection unit 3. In the case where the frequency is detected to be within the acquisition range at step S3, the type of the received video signal is determined using the clock signal frequency that is analyzed at the synchronization frequency analysis unit 4 and AVI information that is guide information included in the received signal. The video signal obtained at the HDMI terminal 1 is digital video data (DTV signal), and the digital video data of the determined type is supplied to a processing system at a stage subsequent to the signal detection unit 3.
WO2002/078336 discloses details of the HDMI standard.